Recently, medical investigations into nerve cells and the possibility of using nerve cells as electric elements have been actively pursued. When nerve cells are active, action potential is generated. This action potential arises from a change in ion concentration inside and outside the cell membrane which is accompanied by a change in ion permeability in nerve cells and thus from the change in cell membrane potential accompanied thereby. Therefore, measuring this potential change accompanied by the ion concentration change (that is, the ion current) near the nerve cells with electrodes enables the detection of activities of nerve cells or nerve organs.
In order to measure the above-mentioned potential arising from cell activities, it is possible, for example, to insert an electrode comprising glass into an area of cells to measure extracellular potential. When evoked potential due to stimulation is measured, a metal electrode for stimulation is inserted together with a glass electrode for recording. However, measurement by the insertion of these electrodes has the possibility of damaging the cells, and measurement over a long period of time is difficult to carry out. In addition, due to restrictions of space and the need for operating accuracy, multipoint simultaneous measurements are also difficult to carry out.
Therefore, the present inventors developed a planar electrode comprising an insulation substrate and a multiplicity of microelectrodes and their drawer patterns formed thereon with the use of a conductive material, and cell culture could take place on that surface (disclosed in Laid-open Japanese patent application Nos. (Tokkai Hei) 6-78889 and 6-296595). With this planar electrode, multi-point simultaneous measurements of potential change can be carried out without being affected by restrictions of space at a plurality of points with a short electrode-to-electrode distance. Also, this electrode enabled long-term measurement.
However, a measurement apparatus which can efficiently use this kind of planar electrode, conduct measurements accurately and efficiently, and improve the arranging of measurement results has been strongly desired. Therefore, it is an object of this invention to provide a cell potential measurement apparatus which is capable of accomplishing these needs in the art.